Spring assembly for carbon brush holder



June 24, 1958 J. F. NOTTELMANN ET AL 2,840,734

SPRING ASSEMBLY FOR CARBON BRUSH HOLDER Filed Sept. 4, 1956 [ml enters.-Car/ E 5,0260%)? John F Waite/27722727,

The/r ,4 ttorn ey Unite States Patent SPRING ASEMELY FQR CARBON BRUSHHQLDER John F. Nottelmann and Carl E. Spaeder, Erie, Pa., assignors toGeneral Electric Company, a corporation of New York ApplicationSeptember 4, 195?, erial No. 607,736

3 Claims. (Cl. 31-246) The invention described herein relates to aspring assembly adapted for use with a brush holder attached adjacentthe commutator of a dynamoelectric machine.

The object of our invention is first, to provide a spring assembly whichwill remain captive on the brush holder during the time an operator isengaged in replacing a carbon brush; second, to prevent the springassembly and brush from becoming detached from the holder when thelatter is subjected to shock; third, to retain the biasing portion ofthe spring within the holder in the event of breakage and therebypreclude it from rotating parts of the machine; fourth, to provide aspring assembly designed in a fashion to permit an operator to eifectreplacement of an old brush by using only one hand for the operation;and finally, to obtain additional advantages as will be apparent fromthe descriptive portion of the application describing the invention.

The prior art discloses the concept of utilizing various types ofsprings for urging a current collecting brush into contact with arotating commutator. More recent developments in the spring field haveresulted in the development of a spring which is pro-stressed so as tonaturally wind into a free tight volute. Springs of this type have beensuccessfully used in baising a carbon brush into contact with acommutator by attaching one end of the spring adjacent the lower end ofthe brush holder while the other end, which assumes the form of a helix,is arranged for contacting the upper portion of the brush. The pressurethereby extended by the spring causes the brush to engage the coppersurface of the commutator at a constant predetermined pressurethroughout the life of the brush.

In spite of the good results achieved by the use of this type spring,certain disadvantages result from its use when not properly applied to abrush holder. It is known for example, that if the machine containing abrush holder is subjected to shock, the brush and in some instances thebiasing spring, are caused to be dislodged from their mounting in thebrush holder thus making the machine and associated equipmentinopeartive. Furthermore, as the carbon brush wears to a minimum point,the biasing spring occasionally breaks from its mounting because of thestrain created at its point of attachment on the inner portions of thebrush holder, thereby placing the broken part in a position to damagethe commutator in the event it falls through the opening in the bottomof the brush holder. A still further disadvantage is that the prior artdesign of spring assemblies does not contain features capable ofeleminating the tension in the spring, While simultaneously making thespring assembly captive on the brush holder body, during the brushreplacement process. As a result, both hands of the operator must beused thereby increasing the danger of electrical shock and subjectinghim to the hazard of a flying spring.

In carrying out our invention, we eliminate the above describeddisadvantages by providing a backing member curved at its lower end forreceiving a pre-stressed spring arranged to be unwound in a manner toexert a constant predetermined pressure on a brush in the brush holderbody. The upper end is bent in a manner to extend a distance above thebrush holder body and to overlie the opening for the brush so as toprevent ejection thereof under certain conditions of operation of themachine. The backing member is additionally provided with a secondspring arm equipped with a projecting tab arranged to engage a detent inthe brush holder for locking the spring assembly on the latter, the armfurther serving to make the assembly captive on the brush holder whenthe tab is disengaged from its locked position.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which we regard as ourinvention, it is believed the invention will be better understood fromthe following description taken in connection with. the accompanyingdrawing in which:

Figure 1 is a view in elevation showing a brush holder having a carbonbrush urged into contact with a commutator by the spring assembly ofthis invention;

Figure 2 is a plan view of the device shown in Figure 1;

Figure 3 is a view in elevation showing the captive arrangement of thespring assembly during the time when a new brush is being inserted inthe brush holder;

Figure 4 is a perspective view of the spring assembly shown in Figures 1through 3;

Figure 5 is a modification of the spring assembly shown in Figures 1through 4 and is shown mounted in a brush holder and in an operativeposition;

Figure 6 is a view similar to Figure 5 showing the position of thespring assembly when in an inoperative position;

Figure 7 is a perspective view of the spring assembly shown in Figures 5and 6;

Figure 8 is a modification showing still another spring assembly adaptedfor use with a different type of brush holder;

Figure 9 is a perspective view of the spring assembly of Figure 8 shownin an inoperative position.

Referring now to the drawing wherein like reference characters designatelike or corresponding parts throughout the several views, there is shownin Figures 1 through 3, a brush holder 12 arranged for positioningadjacent a commutator 14 for a dynamoelectric machine. The brush holdercomprises a square-like hollow member provided with a bracket 16 adaptedfor attachment to a supporting structure and oppositely disposed fromthe bracket is a connector 18 designed for receiving the wire shunt of acarbon brush. As shown in Figure 2, the main body of the brush holder isprovided with a pair of chambers 20 and 22 for respectively receiving acarbon brush 24 and spring assembly 25 arranged for coaction therewith.A. side of the brush holder 12 is, equipped with an opening 26 whichserves in part, to form a projection 27 for a purpose hereinafterdescribed. The particular brush holder generally described above doesnot comprise a part of this invention since the same is disclosed andclaimed in the application of Eugene W. Arsenault and John F. Nottelmannfiled concurrently here- Withand assigned to the same assignee as thisinvention.

As aforementioned, this invention is directed to the spring assembly,and as shown in Figure 4, comprises a spring 28 riveted to an inwardlyturned spring receiving portion 29 of a backing member 36. Riveting ofthe spring to a curved portion of the backing member serves twoimportant functions; namely, that it permits the spring to become loadedmore quickly than if it were attached to a straight portion of thebacking member 39, and because of its position when fully wound, it isadapted to give additional wearing depth to the brush which it urgesinto contact with the commutator 14. It will be noted that .and carbonbrush. The purpose of this retainer is to prevent the brush and/orspring from being ejected out of the brush holder in the event thelatter is subjected to severe shock encountered during unusualapplications of the machine. It further prevents the spring from beingunduly extended and becoming damaged. This simple but importantexpedient eliminates the necessity for providing means exterior to thebrush holder for assuring retention of the brush in the brush holderbody under all conditions of operations.

The structure thus far defined relates to that portion of the springassembly utilized in holding the brush in the holder body. The followingdescription is directed to parts used for locking the spring assembly onthe holder and for making it captive during brush replacement. Re-

ferring to Figure 4, it will be seen that a second spring element 36 iswelded or otherwise afiixed to the backing member 30 and is providedwith a reversely bent arm 38 arranged to engage that part welded to thebacking member 30. The arm 38 is pre-stressed or pre-loaded in such amanner that it exerts pressure in the neighborhood of 2 p. s. i. on thebacking member 30 so as to firmly anchor and add stability to the springassembly by holding the assembly against its seat on the brush holder Ibody, and for making the spring captive during brush replacement. Theend of arm 38 which contacts the brush holder body is bent around an aresomewhat greater than 180 so as to preclude the sharp end thereof fromdigging into the holder body during removal of the spring assembly fromthe brush holder. Spring element 36 is provided with a tab 40 located adistance below part 41 sufiicient to engage projection 27 when thespring assembly is inserted in the brush holder body as shown in Figurel. The combined action of the spring element 36 and that of the spring28 acting against the brush, causes the tab to move into position underthe projection 27 thereby firmly locking the spring assembly to thebrush holder.

An important feature of the spring assembly resides in the arrangementof parts effective in preventing disengagement of the assembly from theholder during brush removal and replacement. When the assembly isreleased from its locked position, spring 28 urges the assembly upwardagainst the slight frictional force created by the spring element 36against the outer surface of the holder. Further upward movement causesthe arm 38 to slide into opening 26 and engage surface 43 whereupon itis made captive on the projection 27 pro vided on the brush holder.

The spring assembly is further designed to have a clearance a betweenthe top of the brush holder body and the under side of part 41 of the,spring assembly in order to prevent the assembly from engaging thecommutator in the event spring 28 is broken or otherwise detached fromthe backing member 30.

In operation, after a new brush is inserted in the brush holder, springelement 36 of the spring assembly is flexed outwardly and slid over theprojection 27 provided on the top of the brush holder body. Furthermovement in a downward direction, as shown in Figure 1, causes the arm38 to engage the outer surface of the brush holder body while the spring28, at this time, is caused to engage the brush. The biasing action ofspring element 36 and spring 28 as above mentioned, causes the tab 40 toassume a position beneath the projection 27 thereby locking the springassembly in an operative position.

4 When it is desired to replace a brush or otherwise remove the springassembly from the holder, the assembly is pushed down and forwardly atthe top to disengage the tab from its projection which permits theassembly to move upwardly until the arm 38 engages the projection 27provided on the brush holder body. As shown in Figure 3, the springassembly can be rotated in a clockwise direction to remove it from aposition above the brush holder body for facilitating insertion of a new'brush. A distinct advantage obtained from this design of springassembly is that the above described operation can be manually performedby an operator using only one hand and therefore eliminates to a largedegree the possibility of electrical shock to which he otherwise wouldbe subjected. I

The modification shown in Figures 5, 6 and 7 is the same as thatdescribed above except for the design of arm 38 on the bottom of springelement 36. Inthis species, the arm is bent outwardly and is providedwith a round smooth surface to prevent the arm from digging into theside of the brush holder during spring assembly removal. However, as inthe foregoing embodiment, it will snap into the opening at the top ofthe holder thereby permitting the spring assembly to be rotated out ofposition without disengaging it from the holder when a new brush isinserted therein.

The modification shown in Figures 8 and 9 is different from thosepreviously disclosed in that the spring element is of an entirelydifferent design but is arranged to serve substantially the samefunction and in somewhat a different manner. As shown, the springelement 36 is provided with a hook 44 arranged for positioning over thelower exposed surface of the brush holder body while the upper end 4-6is curved back on itself in the manner of a hairpin to hold the springassembly in a fixed position relative to the brush holder body. The

hook 4d at the bottom part of the spring assembly serves to prevent thebacking strip 30 from moving into a position where it could foul brush24. The spring assembly is released by pressing down and pullingbackward to unlatch the hook 4.4 from the bottom of the brush holder,whereupon the biasing action of spring 28 causes the assembly to moveupwardly until the hook slips into opening 48 and catches on theprojection 50 provided adjacent the top of the brush holder body. Thespring assembly at this time is held captive and assumes the positionshown in Figure 9 of the drawing. In the event it is desired to removethe brush further, itis merely unhooked a second time and completelyremoved from the brush holder body. The spring assembly in thismodification, does not remain captive with the brush holder while abrush is being changed.

It will be evident that many modifications and variations are possiblein light of the above teachings. For example, it is not absolutelyessential to successful operation of the device that the spring elementassume a specific configuration as evidenced by the different types ofspring elements disclosed herein. It is therefore to be understood thatwithin the scope of the appended claims the invention may be practicedotherwise than as specifically described.

What we claim as new and desire to secure by Letters Patent of theUnited States is: a

1. A spring assembly adapted for use with a carbon brush holdercomprising a backing member having oppositely disposed ends 'turnedinwardly on the same side of said member, a coil spring rigidly attachedto one end of said backing member to permit the volute of said coilspring to rest on one of said inwardly turned ends and thereby relievestrain created 'by said spring at the point of attachment on saidbacking member, and locking means afiixed to said backing member forcoacting with a brush holder to prevent accidental dislodging of saidspring assembly therefrom and for retaining said spring assembly captiveon said brush holder during the time that a new brush is being insertedtherein.

2. A spring assembly for carbon brush holder comprising a prestressedspring of volute construction adapted for exerting a constant forceagainst an expendable carbon brush during the life thereof, a backingmember having inwardly directed ends for respectively providing supportfor said spring and for overlying said carbon brush to prevent ejectionthereof from said brush holder, and means affixed to said backing memberincluding a locking device adapted for securing said spring assembly tosaid brush holder and a spring element for preventing detachment of saidspring assembly from said brush holder during the process of replacing acarbon brush in said holder.

3. The combination according to claim 2 wherein said spring element isprovided with a reversely bent end for facilitating engagement with aprojecting portion on said brush holder and thereby prevent removal ofsaid spring assembly during the process of replacing the brush in saidholder.

4. The combination according to claim 2 wherein said spring element iscurved outwardly from said backing member to effect mounting of saidspring assembly on asid brush holder and to prevent removal therefromduring the process of inserting a new brush in said holder.

5. A spring assembly adapted for use with a carbon brush holdercomprising a backing member having an inwardly directed end forreceiving a pro-stressed spring adapted for urging a carbon brush intocontact with a commutator, the other end of said backing member beingarranged to overlie said carbon brush to prevent ejection from saidholder, a second spring element rigidly affixed to said backing memberand provided with an outwardly directed tab eflective in locking saidspring assembly to said brush holder, the upper end of said secondspring element being formed in the shape of an inverted U and arrangedto provide a distance between the top of said brush holder and the turnof said U of an amount sufficient to prevent said spring assembly fromcontacting said commutator in the event the spring becomes broken orotherwise detached from said backing member.

6. A spring assembly for a carbon brush holder comprising a prestressedspring of volute construction arranged to exert a constant force againsta carbon brush throughout the life of said brush, a backing memberhaving inwardly directed ends for respectively receiving said spring andfor overlying said carbon brush to prevent ejection therefrom when saidbrush holder is subjected to shock, a second spring element rigidlyafiixed to said 6 backing member having a hook on one end for engagingthe bottom of said brush holder and being provided with a reversely bentmember on its other end for firmly positioning said spring assembly onsaid brush holder.

7. A spring assembly for a carbon brush holder comprising a prestressedspring Wound in the form of a volute and being constructed and arrangedto exert a constant force against a carbon brush throughout the life ofsaid brush, a backing member having inwardly directed ends forrespectively receiving said spring and for overlying said carbon brushto prevent ejection therefrom when said brush holder is subjected toshock, a second backing member rigidly afiixed to first backing memberand having an end reversely bent in a manner to engage said brush holderand firmly position said spring assembly therein, the other end of saidsecond backing member having a reversely bent member constructed andarranged to contact a wall of said brush holder to prevent removaltherefrom during operation of said machine but effective to retain saidspring assembly in an inoperative position when a new brush is beinginserted in said brush holder.

8. An improved brush holder for a dynamoelectric machine comprising abox provided with a pair of channels for respectively receiving a carbonbrush and a spring assembly for urging said carbon brush into contactwith a commutator for said machine, a side of said brush holder adjacentsaid channel for holding said spring assembly being formed with anopening, a projecting member on said side arranged to extend into saidopening, said spring assembly comprising a backing member having aspring attached to one side thereof for urging said carbon brush intocontact with said commutator, a second spring member having reverselybent ends attached to said backing member, the lower of said ends beingarranged to engage the bottom of said brush holder on the sidecontaining said projecting member so as to firmly lock said springassembly on said holder when said assembly is in an operative positionon said holder, the upper of said ends being arranged to extend over thetop of said holder and to exert a pressure thereagainst when in anoperative position, said holder being constructed and arranged to permitsaid lower end to engage said projecting member when said springassembly is moved outward from said holder thereby locking said assemblyon said holder in an inoperative position.

References Cited in the file of this patent UNITED STATES PATENTS2,602,100 McDonald July 1, 1952

